Mercury can support ice in permanently shadowed pockets near its poles, despite its close proximity to the Sun. This collection of MESSENGER images shows areas of Mercury’s north polar region that are in shadow. (Courtesy NASA/JHUAPL/Carnegie Institution/NAIC, Arecibo Observatory)

The NASA MESSENGER mission has found evidence for a significant amount of ice on Mercury, according to three papers published today in Science Express. Although Mercury is the closest planet to our Sun, MESSENGER data suggests that permanently shadowed pockets and craters near Mercury’s poles are cold enough to support water in the form of ice and other frozen volatiles.

LASP developed and built the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) instrument onboard MESSENGER. MASCS detects minerals on Mercury’s surface and determines the abundance and components of its thin atmosphere. MESSENGER instruments that contributed to the recent polar ice discovery include the Neutron Spectrometer and the Mercury Laser Altimeter.

Since it entered Mercury’s orbit on March, 17, 2011, MESSENGER has collected multiple, independent lines of evidence for the existence of the planet’s icy, shadowy craters: It has used spectroscopy to measure hydrogen concentrations, which indicate the presence of water ice; measured the amount of light reflected by its polar deposits; and modeled the surface and near-surface temperatures of the polar regions. The resulting data suggest that ice is the primary component of Mercury’s north polar deposits, and that ice is exposed at the surface of some of the deposits and buried in others.